I research the Irish Family History Foundation's database. It contains 12,000,000 surviving rcds for abt 65% of Irish counties. Rcds are increasingly sparse B4 1840, rare B4 1800.
Note 1 - Without a KNOWN parish, the chance of an ancestor's rcds NOT being in this database is AT LEAST 35%.
Note 2 - Only 1/2 of Co. Cork's rcds are in this database.
Note 3 - The RC church kept control over most parish rcds from Tipperary (north). These are ONLY available thru the Tipperary Family History Research center at a substantial fee (regardless of outcome).
For John O'Malley B 1799 in Co. Mayo with the father's forename unknown, no RC rcds exist. There are a few 18th cent. rcds for two protestant sects.
Co. Waterford rcds aren't in this database yet. Suggest you wait until they are. This may take several yrs.
For John O'Malley B 1838 +/- 1 yr in Co. Cork with a father forenamed John, I found just 1 B rcd. The chance that this is for your ancestor is likely less than 25%.
Google the Foundation's name to lead you to this database. Register, opt to be notified as rcds are added and browse. Pls post your search results to my genforum msg.